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Reference circuit for LTC4215


We are using ADM1278 hot swap controller in our server board schematic. PFA schematic page for reference. But due to the unavailability of ADM1278, we need to find an alternate. We are considering LTC4215 since it is in stock and has similar functionality.

However, in the datasheet of LTC4215 we could only find reference circuit for 16.6 A circuit breaker (page 24). Our application requires 140A current. Would it be possible to share a reference circuit for higher current using LTC4215? Also is it ok to use multiple FETs in parallel connected to GATE pin of hot swap controller to handle high current requirements?

Also, please let us know if any other suitable alternate is available for ADM1278.



  • Hi Avani,

    The ADM1278 is currently not recommended for new designs. Instead we recommend the LTC4281/2. 140A is a lot of current, so the single gate LTC4281 may be adequate, and the LTC4281 should be a direct replacement for the single gate ADM1278. However, if you need a very robust high current solution for 140A and above then I recommend the dual gate LTC4282, which is more complex, but will provide more protection options for high power circuits.

    The DC2442 (LTC4282) demo board provides a good reference design that is close to the 140A spec that you are looking for. The DC2278 (LTC4281) demo board provides a smaller reference design, but the board can probably be modified by soldering additional FETs and changing the BOM to meet your requirements.


  • Thanks a lot for quick reply. I will look into the LTC4281/2 reference design.



  • Hi Nathan,

    We were checking DC2422(LTC4282) reference schematic and how our existing schematic with ADM1278 can be modified for LTC4282. We have a few doubts, about whether we can reuse few components such as FETs and sense resistors from ADM1278 schematic in the new schematics with LTC4282.  This is because we have already ordered FETs and other discretes and it would be great if we can reuse the same in new schematics.

    Please find link for our schematic with ADM1278

    1. The FETs in our original schematic are PSMN0R9-25YLC. We are using total  4 FETs  assuming 140A current limit. DC2422 reference schematic has total 9 FETs with gate2 connected to  8 FETs with MPN PSMN0R9-30YLD and gate1 connected to  single FET with MPN PSMN011-30YL. We understand that the DC2422 schematic is using 'low stress staged start' configuration. We would like to know whether we can use the same 4 FETs from ADM1278 schematic? And whether any other changes would be required in the schematic to use only 4 FETs with MPN PSMN0R9-25YLC? Should we short gate1 and gate2 and go for single MOSFET configuration?

    2.  We are using 3 sense resistors with 0.0005 ohm in ADM1278 schematic to get current limit of 140A. As per the formula given for LTC4282, we have calculated that we would need 6 sense resistors instead of 3 which would give 150 A current limit. (Rsense= 12.5mv/current limit). But it is also mentioned in the datasheet that the default value of 12.5 mv for Vsense can be adjusted through I2C interface. Considering the step size of 3.1mV if we adjust Vsense to 24.9mV through I2C then the 3 sense resistors of 0.0005 ohm would be sufficient for 150A current limit. Is this approach correct?